Abstract:

The present invention provides systems, methods, and apparatus for
processing a lot of substrates in a lithography track system with an
integrate metrology sensor. The invention includes performing a coating
process on substrates; transferring the substrates to a stepper for
alignment and exposure; transferring the substrates to a post-exposure
bake chamber for bake; and performing metrology on the substrates in the
lithography track system. The invention may further include automatically
reworking substrates in an integrated rework chamber within the
lithography track system. Numerous other aspects are provided.

Claims:

1. A system comprising:a lithography track adapted to process a substrate;
andan integrated metrology sensor disposed within the lithography track.

2. The system of claim 1 further comprising an integrated metrology
chamber adapted to support the integrated metrology sensor.

3. The system of claim 2 wherein the lithography track includes a
post-exposure bake chamber and wherein the integrated metrology chamber
is disposed adjacent the post-exposure bake chamber.

4. The system of claim 1 further comprising an integrated rework chamber
disposed within the lithography track.

5. The system of claim 4 wherein the lithography track includes a
post-exposure bake chamber and an integrated metrology chamber adapted to
support the integrated metrology sensor, and wherein the integrated
rework chamber is disposed adjacent the integrated metrology chamber.

6. The system of claim 5 further including a controller coupled to the
lithography track and adapted to direct the integrated rework chamber to
process substrates based on data from the integrated metrology chamber.

7. The system of claim 6 wherein the lithography track is adapted to
process a lot of substrates without separating an associated test
substrate from the lot while the test substrate is reworked.

11. The lithography track of claim 8 further comprising an integrated
rework chamber disposed within the lithography track.

12. The lithography track of claim 11 wherein the lithography track
includes an integrated metrology chamber adapted to support the
integrated metrology sensor and wherein the integrated rework chamber is
disposed adjacent the integrated metrology chamber.

13. The lithography track of claim 12 further including a controller
coupled to the lithography track and adapted to direct the integrated
rework chamber to process substrates based on data from the integrated
metrology chamber.

14. The lithography track of claim 13 wherein the lithography track is
adapted to process a lot of substrates without separating an associated
test substrate from the lot while the test substrate is reworked.

15. A method of processing a lot of substrates in a lithography track
system, the method comprising:performing a coating process on a
substrate;transferring the substrate to a stepper for alignment and
exposure;transferring the substrate to a post-exposure bake chamber for
bake; andperforming metrology on the substrate in the lithography track
system.

16. The method of claim 15 further comprising adjusting the stepper based
on the metrology performed on the substrate in the lithography track
system.

17. The method of claim 16 further comprising processing additional
substrates of the lot in the adjusted stepper.

18. The method of claim 15 further comprising reworking the substrate in
the lithography track system without separating the substrate from the
lot.

19. The method of claim 18 wherein reworking the substrate in the track
includes using an integrated rework system disposed in the lithography
track system.

20. The method of claim 15 wherein the metrology is performed using an
integrated metrology sensor disposed in the lithography track system.

[0002]The present invention relates generally to electronic device
manufacturing systems, and more particularly to lithography tracks in
such systems.

BACKGROUND OF THE INVENTION

[0003]Semiconductor device geometries have dramatically decreased in size
since such devices were first introduced several decades ago. As device
geometries have become more dense, reductions in the spacing between
device elements has occurred. The minimum line widths achieved using
semiconductor lithography systems, sometimes referred to as a critical
dimension (CD) have decreased over time.

[0004]Lithography or photolithography generally refers to processes for
transferring patterns between a mask layer and a semiconductor substrate.
In lithography processes for electronic device fabrication, a silicon
substrate is typically uniformly coated with a photosensitive material,
referred to as a photoresist, for example, in a cluster tool. A
scanner/stepper tool may be used to selectively expose the photoresist to
some form of electromagnetic radiation to generate a circuit pattern
corresponding to an individual layer of the integrated circuit (IC)
device to be formed on the substrate surface. Generally, the photoresist
film is selectively exposed using a mask layer that preferentially blocks
a portion of the incident radiation. Other alternative or additional
methods may be employed. The portions of the photoresist film that are
exposed to the incident radiation become more or less soluble depending
on the type of photoresist that is utilized. In some systems, a
developing step dissolves the more soluble regions of the photoresist
film, producing a patterned photoresist layer corresponding to the mask
layer used in the exposure process.

[0005]The precision with which the patterns are developed on the
semiconductor substrate impacts the CDs present on the substrate, likely
impacting device performance. Overdevelopment may result in an increase
in line widths, whereas underdevelopment may result in portions of the
photoresist layer not being removed as desired. This is one example of a
part of the lithography process that may result in the need for rework.
Many others exist. Various methods have been used, for example, to
determine the endpoint of the developer process and/or to identify
devices formed on the substrate whose dimensions are outside of the
specified/acceptable range and thus require rework. However, these
methods are typically manual, significantly impact the throughput of the
system, and typically require sample substrates to be removed from the
system to perform one or more metrology and rework processes. Therefore,
there is a need in the art for improved systems for detecting the need
for re-work and improved methods of automating the same.

SUMMARY OF THE INVENTION

[0006]In some embodiments, the present invention provides a system that
includes a lithography track adapted to process a substrate; and an
integrated metrology sensor disposed within the lithography track.

[0007]In other embodiments, the present invention provides a lithography
track that includes a coating chamber; a post-exposure bake chamber
adjacent the coating chamber; and an integrated metrology sensor disposed
within the lithography track.

[0008]In yet other embodiments, the present invention provides a method of
processing a lot of substrates in a lithography track system. The method
includes performing a coating process on a substrate; transferring the
substrate to a stepper for alignment and exposure; transferring the
substrate to a post-exposure bake chamber for bake; and performing
metrology on the substrate in the lithography track system.

[0009]Numerous other aspects are provided in accordance with these and
other aspects of the invention. Other features and aspects of the present
invention will become more fully apparent from the following detailed
description, the appended claims and the accompanying drawings.

[0011]FIG. 2 is flow chart depicting an example method of processing a
substrate according to some embodiments of the present invention.

[0012]FIG. 3 is a block diagram that schematically depicts an example
lithography track system according to some embodiments of the present
invention.

DETAILED DESCRIPTION

[0013]Manuel rework process flows are well known in the electronic device
manufacturing industry. However, due to various factors, automation of
rework processes remains commercially unavailable. The present invention
overcomes a number of these factors to allow rework processes to be
automated in lithography tracks. Using integrated, in situ metrology, the
present invention provides the capability of automatically reworking test
substrates or other substrates which have automatically been identified
as, for example, not meeting critical dimensions (CD) or not meeting
overlay specifications.

[0014]In some embodiments, the present invention provides a lithography
track that includes one or more integrated metrology sensors such that
in-place analysis of the substrates being processed may be made without
having to transfer the substrates to a separate metrology tool. The
present invention further provides process control software, operable to
run on either a controller of the lithography track or a separate host
controller, that is adapted to determine whether a photoresist pattern
should be reworked or meets specifications. This metrology determination
may be applied to test substrates to greatly reduce overall substrate lot
cycle time and thus, increase overall throughput. In some embodiments,
the metrology determination may be applied to any or all substrates being
processed in the lithography track of the present invention.

[0015]The present invention overcomes a number of problems with prior art
rework processes. Test substrates, often prepared with a "focus-exposure"
matrix (FEM), need to be reworked. This rework is conventionally done in
other tools or equipment and requires that the remaining substrates in
the lot associated with the test substrate must wait for the test
substrate, or that the test substrate gets patterned later and catches up
with the associated lot. In either case, extra handling is required and
the process flow is complicated in the manufacturing execution system
(MES). Further, in conventional systems, metrology (e.g., CD and overlay)
measurements are not typically made on other substrates in the lot
associated with the test substrate. However, using the lithography track
with integrated in-situ metrology of the present invention, the data
required to make pass/fail decisions is easily and quickly acquired and
made available for such use. The present invention further includes an
in-situ rework capability integrated with the track to allow rework
without the extra handling and flow complications of conventional manual
process flows.

[0016]Turning to FIG. 1, an example of a typical prior art lithography
process 100 is depicted. In step 102, a coating process (e.g., BARC
(i.e., bottom anti-reflective coating), resist, top coat, etc.) is
performed. In Step 104, the substrate is transferred to a stepper for
alignment and exposure. If the substrate is the first in the lot, a FEM
pattern may be formed. In step 106, the substrate is retrieved from the
stepper, post-exposure bake (PEB) is performed, and the substrate is
developed. In step 108, the substrate is transferred to stand-alone
metrology tools to measure CD and overlay of the pattern. In step 110,
the stepper is adjusted for the correct exposure dose and alignment
offset based on the metrology. In step 112A, the test substrate is
reworked (e.g., ashing and/or wet clean processes are applied).
Alternatively, if the substrate is one of the remaining substrates in the
lot associated with the test substrate, in step 112B, the substrate is
processed by the track and the stepper. In step 114, the test substrate
is processed by the track and the stepper. Thus, the prior art method of
reworking the test substrate (or any other substrates in the associated
lot) requires additional handling and cycle time because either the
performance of track and scanner processing step 114 on the test
substrate must wait or step 112B, processing of the other substrates in
the associated lot, must wait. In step, 116, the substrate lot is
recombined and is moved to the next step in the process flow.

[0017]Turning to FIG. 2, an example of a lithography process 200 according
to embodiments of the present invention is depicted. In step 202, a
coating process (e.g., BARC, resist, top coat, etc.) is performed. In
Step 204, the substrate is transferred to a stepper for alignment and
exposure. If the substrate is the first in the lot, a FEM pattern may be
formed. In step 206, the substrate is retrieved from the stepper, PEB is
performed, and the substrate is developed. In step 208, CD and overlay of
the pattern is measured within and by the track using integrated
metrology sensors. In step 210, the track sends the stepper the data
(determined from the integrated metrology) to adjust for the correct
exposure dose and alignment offset. In step 212A, without being separated
from the associated lot, the test substrate is reworked (e.g., ashing
and/or wet clean processes are applied) in the track using an integrated
rework system and then, in step 212B, processed by the track and the
stepper. CD and overlay are measured using the integrated meteorology.
Alternatively, if the substrate is one of the remaining substrates in the
lot associated with the test substrate, the rework step 212A is bypassed
and in step 212B, the substrate is processed by the track and the
stepper. CD and overlay are measured on all substrates using the
integrated meteorology. In step 214, the substrate lot is moved to the
next step in the process flow.

[0018]Thus, by using the integrated metrology and automated rework
chambers, the overall cycle time may be reduced and less handling of the
substrates is required as compared with conventional processes.

[0019]Turing to FIG. 3, an example lithography track system 300 according
to embodiments of the present invention is depicted. An inventive
lithography track system 300 may include a lithography track 302 which
includes a coating processing chamber 304, access to a stepper 306, a
post-exposure bake chamber 308, an integrated metrology chamber 310, and
an optional integrated rework chamber 312. A controller 314 is coupled to
the lithography track system 300 and operative to use the data from the
integrated metrology chamber 310 to control or adjust the stepper 306
and/or other components.

[0020]In some embodiments for example, the integrated metrology chamber
310 may include and support a scatterometer of the spectroscopic
reflectometer type. This device uses a light source to supply a
high-power, broadband, well-collimated beam which is directed to a beam
splitter, which reflects the beam towards the substrate to be measured. A
microscope objective lens focuses the beam onto the substrate and
collects the reflected light, directing it through the beamsplitter to a
mirror, which reflects the light to a grating. The grating disperses the
light onto a detector, e.g., a cooled CCD array. The output of the CCD
array represents a spectrum of the reflected light, i.e. a measurement of
intensity as a function of wavelength, which can be used to deduce
parameters of a structure on the substrate, e.g. the linewidth of a
grating, in a known manner, for example by comparison with a library of
measurements form test structures or spectra calculated by simulation.

[0021]In operation, the present lithography track system 300 may be used
to perform the methods of the present invention. Although not shown, one
or more robots and/or substrate handling devices operating under the
direction of the controller 314 may be included in the lithography track
system 300. A coating process (e.g., BARC, resist, top coat, etc.) is
performed on the substrates in the coating processing chamber 304. The
substrates are then each individually transferred to the stepper 306 for
alignment and exposure. As indicated above, if the particular substrate
being processed is the first in the lot, a FEM pattern may be formed. The
substrate is then retrieved from the stepper 306, PEB is performed in the
post-exposure bake chamber 308, and the substrate is developed.

[0022]Next, CD and overlay of the pattern is measured within and by the
track 302 using integrated metrology sensors in the integrated metrology
chamber 310. The track 302 sends the stepper 306 the data (determined
from the integrated metrology) to adjust for the correct exposure dose
and alignment offset. Without being separated from the associated lot,
the test substrate is reworked (e.g., ashing and/or wet clean processes
are applied) in the track 302 using an integrated rework system 312 and
then, processed by the track 302 and the stepper 306. CD and overlay are
measured using the integrated meteorology chamber 310. Alternatively, if
the substrate is one of the remaining substrates in the lot associated
with the test substrate, rework system 312 is bypassed and the substrate
is processed by the track 302 and the stepper 306. CD and overlay are
measured on all substrates using the integrated meteorology chamber 310.
In some embodiments, metrology sensors may be disposed in additional
locations along the track 302 and/or stepper 306 in addition to within
the integrated meteorology chamber 310.

[0023]The foregoing description discloses only exemplary embodiments of
the invention. Modifications of the above disclosed apparatus and method
which fall within the scope of the invention will be readily apparent to
those of ordinary skill in the art.

[0024]Accordingly, while the present invention has been disclosed in
connection with exemplary embodiments thereof, it should be understood
that other embodiments may fall within the spirit and scope of the
invention, as defined by the following claims.